AC Delco 'SI' Alternator wiring oddity, where is your 'excite' wire ... Your alternator is a classic example of a Delco Remy SI series alternator... Just like I show in all my drawings and wiring diagrams.

19020900 24SI New Alternator | Product Details | Delco Remy If the original model plug regulator is NOT in use, therefore not connected with an OEM harness, the model can be replaced by this proposed replacement part ...